I was flummoxed when I heard that this thing is APS-C only. Why?! If this is a premium lens aimed at serious shooters, why go crop? This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys? That would likely have a larger interest level.

I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!!

The 17-55 could easily have been a 15-50. The 18-35 could have been a 15-30.

Well, if you're willing to pay about 40% more, than 15-85 is gettable instead of 17-85. But, if you start adding 40% to all the prices of the Sigma/Tamron/etc lenses that go 17-50, most people wouldn't but them. It's one thing to get a $4-500 OS f/2.8 zoom; but by the time it's $6-700 there are other ways to go. Likewise if the 17-55 was a 15-50 that cost $1500. Going those extra few mm's means bigger glass, and more expensive lenses.

If it was so easy to make 15mm zooms, then why is Canon the only one that does?

Oh, brother.

You realize that 10-20, 10-22, 8-16 and 12-24 are all available in crop lenses, right?

Going a little wider isn't that big a deal, especially if you maintain the total zoom ratio. Longer is harder with fast lenses as the absolute aperture diameter has to be larger, which is why 70-200s are so expensive.

This is great for crop shooters. However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor. This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. However, lens and sensor imperfections actually favor the larger format sensor, so don't expect this lens to give anything as good as the 24-70 f/2.8 original or the tamron.

Still, its great improvement for crop shooters (if it keeps up with recent Sigma trends), and should be relatively compact.

(*1) This considers photon shot noise only and assumes photos are rescaled to same resolution when printed.(*2) At non-macro distances

I was flummoxed when I heard that this thing is APS-C only. Why?! If this is a premium lens aimed at serious shooters, why go crop? This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys? That would likely have a larger interest level.

I was flummoxed when I heard that this thing is APS-C only. Why?! If this is a premium lens aimed at serious shooters, why go crop? This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys? That would likely have a larger interest level.

I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!!

I'm actually tremendously interested in a new version of their 24-70/2.8 and who knows, maybe something like a 24-90/4. The Tamron is quite good, but Sigma looks like they don't want to be a "second choice" anymore. I love when 3rd-party manufacturers deliver such quality; they set you free from this or that system.

This is great for crop shooters. However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor. This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. However, lens and sensor imperfections actually favor the larger format sensor, so don't expect this lens to give anything as good as the 24-70 f/2.8 original or the tamron.

Still, its great improvement for crop shooters (if it keeps up with recent Sigma trends), and should be relatively compact.

(*1) This considers photon shot noise only and assumes photos are rescaled to same resolution when printed.(*2) At non-macro distances

Depending on the price point, the difference between a FF + 24-70 and DX + 18-35 might be what is truly impressive. This lens is not going to reach anything tremendous from an absolute perspective, but it's going to narrow the gap between crop and FF. Actually, I think it would make for an amazing travel lens since it would eliminate the need of a fast prime. If you want to travel light and bring only a crop body and one lens, you either go for a usual standard zoom and live with the slow aperture or you go with something like this.

I'm really excited about this lens, and I don't even own a crop body. I'm excited about the implications for the future. If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics. Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers. The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.

I know what you mean. It seems like future optics have to get better and better and it's pretty exciting to see unfold before you.

Even if it doesn't live up to all the hype and press, if it does manage f/1.8 across the entire focal/zoom range that's pretty exciting in and of itself. It makes you a bit excited about that possibly happening in FF lenses, but I seem to think that it's far quicker to happen with the APS-C lenses than the FF, due to the APS-C sensors design and size compared with the FF...

I'm really excited about this lens, and I don't even own a crop body. I'm excited about the implications for the future. If this lens can be produced and has good optics (which will be the real issue), it raises so many interesting implications for the future.

A 27-55mm, or even 27-50mm f/1.8 FF lens would be absolutely amazing if it had good optics. Once the technology is out there, reverse engineering means that this advance will soon be in the hands of other manufacturers. The very nature of putting out an APS-C only lens means that the price has got to be somewhat reasonable, as there are not (to my knowledge) many APS-C lenses over a thousand dollars US.

+1 Though this might not be the most appealing range for most, it's a game changer that will influence really good stuff in the near future. I'd be happy with something like a 24-50mm f/2 for full frame actually, seeing stuff like this being released makes me confidently look forward to more developments.

I was flummoxed when I heard that this thing is APS-C only. Why?! If this is a premium lens aimed at serious shooters, why go crop? This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys? That would likely have a larger interest level.

- A

If I'm not mistaken, this has to do with technical & feasibility issues. Actual lens diameter for crop can be smaller than for ff bodies, thus making it easier to produce f/1.8. Or am I completely wrong right now?

I was flummoxed when I heard that this thing is APS-C only. Why?! If this is a premium lens aimed at serious shooters, why go crop? This is not a screaming need for the relatively few APS-C guys who spend big money on glass (i.e. birders, sports guys), so I can't make heads or tails of this.

Why not push for (idk) a 24-50 F/2 for the FF guys? That would likely have a larger interest level.

- A

If I'm not mistaken, this has to do with technical & feasibility issues. Actual lens diameter for crop can be smaller than for ff bodies, thus making it easier to produce f/1.8. Or am I completely wrong right now?

You're not wrong, but for those saying this is no big deal, I disagree. This is something that has not been done before for either crop or FF (an f/1.8 zoom), so to dismiss it outright is absurd. Yes, developing for full frame is more challenging, but this is clearly a step in the right direction and will put more pressure on Canon. As a consumer, I see that as a good thing

I think what has happened is that Canon's pricing policies have become SO absurd that is has given some astute tech. and money managers at Sigma the ability to realize that they have a lot more wiggle room to make a great product and still be super competitive in price to big read. (it also shows how ridiculous Canon's pricing has become). I do not own a crop body either, but I do LOVE the appearance of this lens! Hope the IQ and price/performance ratio are right up there with the Sigma 35mm, f/1.4 that I own and absolutely love. This can be nothing but good for all of us! Can't wait to see what the next lens is in the new Art Line!!!!!!!

Me too, me too!!

And a few more thoughts:

1. Haven't seen a single complaint yet about no IS.

2. This is another brick in the foundation I've been building for APS-C as a viable, long term sensor format -- and the coming of an extraordinary 7D2 that just about everyone will want!

3. What are the video implications of this lens? Surely there must be some (don't know since I don't video).

4. Talking about "wiggle room," this seems to go right at Canon's 17-55mm f/2.8, a great lens but one that seems overpriced. (Although the Canon lens does have IS.) If the Sigma is priced under $1K, it may give Canon some pain. And if it's really sharp at f/1.8 it will provide better subject isolation than the Canon at f/2.8 (let the bokeh wars begin!).

I'm pretty sure aperture is a fixed definition, doesn't matter if it's a compact P&S or medium format, the same numbers will give the same size lens (focal length divided by lens diameter = aperture) http://en.wikipedia.org/wiki/F-number

Compact cameras usually have a flange distance of close to nothing, a 3mm f2 would still be tiny, but with the extreme crop factor of compacts they make it seem like a normal camera.I just realized that it's probably the form factor of the camera that dictates the size of the sensor on those (the larger the sensor the larger the lenses, and thus the larger the camera would need to be).